ATTACK OF THE CRAZY ELECTRONICS!!!

[BDI]

So I just figured out all the various 'tronics and tonal tonics that are going into my next project. It's basically a Jerry Garcia/David Gilmour mashup stratocaster  :glasses9:. I don't know if there's anybody here who really enjoys playing with guitar electronics, but I'm pretty proud of my diagram, so I thought I'd share. I was also wondering if somebody who's good with wiring could "proofread" the diagram to make sure I didn't design any mistakes before I start a-solderin'...

A little explaination:
-Three single coils (Fender CS '69's), with neck-on switch and series/parallel switch between the bridge and middle
-An active buffer that lowers the impedence, preventing signal loss from long cable runs. (actually an exact clone of the preamp in Garcia's "Tiger" http://www.wald-electronics.com/wald-electronics_shop/tiger_preamp_clone.html )
-An on-board effects loop, ensuring pedals get maximum signal
-Respective bypass switches for the buffer and OBEL
-Kill switch
-Master Volume and Tone

Just a little on the complicated side, but hey, the hardest part's already done! Here's the pictures (I think I missed a switch on the full mockup but you get the idea):

 

[iamdavidmorris]

The kill switch looks correct.  :icon_thumright:

 

[Shadow]

Two things:

- You using a Y cable for the on-board effects loop?
- Are you going for switches or putting some on p-p pots?

 

[BDI]

Yes to the Y-cable. I have a (1)stereo-to-(2)mono cable that I bought a while ago for running two amps. It should be perfect for this.
I'm going to do switches. I never really liked push/pull pots, I guess it's just a personal preference. I measured out the strat control cavity and I'm going to have to do a little routing under the guard to fit all the switches and buffer. I'm also going to install a battery box on the back.

Thanks for reading/commenting!

The kill switch looks correct.  :icon_thumright:

Oh, whew! At least I got something right!  :laughing7:

 

[Firebird211]

Everything seems ok to me, except I'm not sure if you intentionally labled the volume pot 25K ohms.  That is one crazy bugger you got there.  Hopefully you won't get any bad interactions between settings, but I don't see any potential problems just by looking at it.  There is another Gilmourish strat on the forum called the Black Cat Strat, and it is a freaking gorgeous recreation of it.  Yours has all the electronic goodies, though.  
http://www.unofficialwarmoth.com/index.php?topic=11714.0

 

[BDI]

Wow! That Black Cat really is just something else, eh? Very cool...
And the 25k volume has something to do with the buffer. It's the value suggested by the manufacturer and the value Jerry had in his guitars (the ones with the buffer, anyway). I'm still waiting for a few more components, but I should be getting going within the next few days. Can't wait!  :toothy10:

 

[Firebird211]

Wow! That Black Cat really is just something else, eh? Very cool...
And the 25k volume has something to do with the buffer. It's the value suggested by the manufacturer and the value Jerry had in his guitars (the ones with the buffer, anyway). I'm still waiting for a few more components, but I should be getting going within the next few days. Can't wait!  :toothy10:

That is very weird, but I never delt with the buffer before.  I just though you forgot a zero. :laughing7:

 

[Shadow]

It doesn't appear to have any problems... Looks good. Only thing would be make sure you have the y cable hooked up the right way. Other than that it should be fine.

Also, 25K does sound right, I know that there's 25K's in EMG setups as well...

 

[line6man]

There are a number of things wrong with your diagram.

First off, the killswitch needs to be wired to the output jack, not the input of the volume pot.

Second, it would be preferable to wire the killswitch to disconnect the signal from the jack as well as short the output, rather than simply shorting the output, because it is not the best idea to have your preamp driving a zero Ohm load when you mute the output.

Third, it would be preferable to wire your active/passive switch like this:

The way you have it leaves the input of the preamp connected to the signal at all times. While the preamp should have a fairly high input impedance which should have a minimal impact on the LCR of the pickups, the input impedance parallel to the pickups will drop to 1/([1/Z1]+[1/Z2]) in passive mode, whereas Z1 is the preamp input impedance, and Z2 is the input impedance of whatever the guitar is plugged into.

Fourth, a 25K volume pot will only work properly with a low impedance signal. In passive mode, you will have a high impedance signal feeding into the volume pot, so it's relatively direct resistance parallel to the pickups will cause a big drop in output and treble. It would be preferable to move the volume pot to before the input of the preamp, so that it will always see a high impedance signal.

Edit: The volume pot should also be a 250K or 500K, if you put it before the input of the preamp.

 

[Shadow]

Also, don't you usually want a volume control before your effects? I mean it would be more player preference, but it gives you more control over some of your effects .

 

[BDI]

That actually makes a ton of sense. I didn't think of what the volume would do in passive mode. Thanks for the tip on the switches as well. I think I'm going to just leave out the passive/active switch, because the benefit of having the loop on-board is to have the volume come after it (It allows the effects to get the full output of the pickups and then use the guitar volume as a master before the amp- I guess it's debatable wether it's a benefit. This is how Jerry did it though). I guess if I want a plain, purely-passive strat, I'll just play my other one  :icon_biggrin:. I'll look into changing the killswitch, too. Is there a way to fix it like you say, with just the two terminals the switch has (it's momentary usually-open)? What's the danger of connecting it like it is (Buffer with no load when engaged)?

Thanks for EVERYONE'S input! That's why I love the internet and forums/people like you guys.

 

[line6man]

I'll look into changing the killswitch, too. Is there a way to fix it like you say, with just the two terminals the switch has (it's momentary usually-open)? What's the danger of connecting it like it is (Buffer with no load when engaged)?

It could be perfectly fine, but depending on the design of the output stage, it might not be the best thing for the preamp over time.
Think of it like shorting the speakers out on your amp. (But at a much lower current, of course.)

 

[BDI]

Could the switch be moved somewhere else? Or would it do the same thing no matter where it's placed? For example, if I moved it before the preamp:

 

[line6man]

Could the switch be moved somewhere else? Or would it do the same thing no matter where it's placed? For example, if I moved it before the preamp:

It's questionable.
On the one hand, with the preamp's input at ground potential, and the output running a low impedance signal, the guitar should be pretty damn quiet, however, if the preamp itself is noisy, that noise will be audible in the output. Remember, also, that your preamp feeds the effects loop thing, which, depending on what is connected to it, will further increase the noisefloor.

You really would be better off with an SPDT switch which will allow you to both disconnect the preamp, and short the output jack.
Was there something special about the switch you were using? I'm sure you can find another switch with identical specs in SPDT form.

 

[line6man]

Also worth noting, if you put your tone control after the preamp, 250K and 0.022uF will not be good values. A 250K pot will have little effect on the signal until toward the end of the rotation, and 0.022uF is a fairly low capacitance given the lower output impedance of the signal. You will want to increase the capacitance to get the same treble cutting effect you would expect of a tone control in a passive circuit. 0.1uF would be a start.

I would keep the tone control before the preamp, personally.

 

[BDI]

Man, how could I have missed all this stuff? Looking back at the picture, I'm a little embarassed  :binkybaby:. I don't even know why I drew in a .022 cap, when I usually put .047's with single coils. Would it sound better to have the cap value even higher than the .1 you mentioned, or is that a  personal taste/ears thing? I think I'll go with the .1, I've got a few lying around. And it makes more sense to put the tone before the preamp- I can adjust the highs going to the effects, more versatility, etc. Nothing special about the SPST momentary, except that I already had it in my big random electronics box. I'll just have to spend the whopping 2 whole bucks to get a SPDT.

So the design below would work?

Man I owe you lunch & a beer or something. Thanks so much

 

[BDI]

Wait. If it's before the buffer, not after, it should still be .022-.047, correct?

 

[Firebird211]

Wait. If it's before the buffer, not after, it should still be .022-.047, correct?

That looks correct to me, but according to your taste in tone control.  After the output would be a different story.  The killswitch makes much more sense now.  I thought some of the strange arrangement in wiring was according to the Garcia wiring.  I could recognize the Gilmour features, but I only looked your circuit over for a few min before heading to bed. :doh:  Best to catch all the bugs now before you wire the whole thing.

 

[BDI]

Yeah I can't imagine what I would have done if I had just wired it up the way I had it. I compiled all the various diagrams that I found into something that I liked, without really checking to see how it would all work together :doh:. I guess that's what makes designing these things a bit tricky. Thanks for all your input!

 

[line6man]

So the design below would work?

Almost.

Swap the volume pot's output with the output jack's tip terminal on the killswitch. That way the output jack can short out, and the signal will disconnect, when you use the killswitch.
The tone control is also backwards. Try it like this:

As you've already realized, with the tone control before the preamp, you can use your regular capacitor values again. A 0.022uF or 0.047uF cap will work the same as it would in any other Strat.
To answer your question on cap values, the higher the value, the lower the frequency cutoff point, so assuming all other factors remain the same, the higher the value, the more treble cut you'll get when you use the tone control. There are no rules to it, it is indeed a personal preference.